Gel freshener and method of making the same

ABSTRACT

A transparent gel air freshener and method of preparing the same. The gel composition comprises an aqueous gel, a fragrance, a surfactant and a co-solvent. The gel is transparent and free from visible particles and inhomogeneities, has a uniform texture and a continuous structure, and includes volatile scented components. The gel is capable of suspending solids such as botanicals therein for decorative effect. The method provides for preparation of a such a gel air freshener, including the suspension of botanicals therein, while maintaining the clarity, texture, and structure of the gel. The method includes the steps of preparing a gel composition and cooling the gel composition. Botanicals may be added to the gel composition when it has gelled enough to support the botanicals on the gel surface.

This application is a division of application Ser. No. 08/696,493, filedAug. 14, 1996, now U.S. Pat. No. 5,679,334.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates generally to a gel composition suitable for useas an air freshener, and particularly a decorative transparent gelcomposition having one or more solid articles suspended therein.

Compositions which release fragrant volatile components into the airhave long been used as air fresheners. Traditionally, such compositionshave been valued for their utilitarian ability to impart a desired scentinto the air and mask stale or unpleasant odors. Within the household,they have found their greatest use in areas where stale or unpleasantodors are most likely to occur, such as bathrooms and kitchens. Thecontainers or dispensers used to disperse these compositions into theair have tended to be more functional than attractive, despite effortsto the contrary.

More recently, scent-releasing compositions have come to be used toextend a room's decor or theme into an additional sensory dimension orto evoke a particular feeling or mood. For example, the scent ofaromatic woods may be used to bring the feeling of the outdoors into thehome, or a spicy apple scent may be used to induce nostalgicrecollections of home-baked pies. The scents used in these compositionstypically are more complex and sophisticated than the heavily perfumed,disinfectant-type scents commonly used in traditional air fresheningcompositions.

The trend toward the use of scented compositions to enhance home decorand ambiance has resulted in increased use of these scented compositionsin areas of the household, such as bedrooms and living rooms, wheretraditional air fresheners are less frequently used. Persons who wish touse scented compositions in these areas of the home, however, may bereluctant to place an unattractive, functional container in these areasof the home. Thus, a need exists for a scented composition that may bepackaged in an aesthetically pleasing container that harmonizes with, oreven enhances, household decor.

Air fresheners have been prepared in the form of pastes or gels tocontrol spills or leaks. These pastes and gels generally have had anonuniform appearance, with breaks or discontinuities in their structureor texture that detract from the appearance of these compositions. Thesediscontinuities are particularly noticeable when the compositions arepackaged in transparent containers. In addition, these air fresheningpastes and gels have tended to have a cloudy or opaque appearanceresulting from the phase separation of the aqueous base components andthe oil-based fragrance components. The cloudy appearance of thesecompositions makes them undesirable for decorative use, particularlywhen they are packaged in transparent containers. The phase separationproblem becomes increasingly difficult to solve when a relatively highfragrance concentration is used in the gel composition. It is sometimespossible to increase the surfactant level in the composition to reduceor eliminate the phase separation. However, this approach often isineffective because the higher surfactant level adversely affects thefragrance-dispersing capability of the composition.

Because scented compositions are finding greater use in living areas ofthe home where their appearance is important, it may be desirable toplace solids within the body of a transparent gel, and particularlywithin a specific region of the gel, to achieve a decorative effect.However, these solids generally will tend to float or sink depending ontheir specific gravity, resulting in an unattractive clumping of thesolids at the top or bottom of the gel. This problem is compounded whenthe gel is intended to be displayed for decorative purposes in atransparent container, because the suspension of the solids in aspecific region of the gel must be accomplished without fracturing orotherwise disrupting the desired smooth and uniform appearance of thegel.

In keeping with the increased emphasis on the natural environment andnostalgic themes, the solids desired to be dispersed throughout the gelmay be botanical specimens, such as berries, slices of fruit, leaves,seeds, flowers, herbaceous sprigs, small branchlets and the like. Thesenatural substances may be adversely affected by the moisture or othersubstances present in the gel. Swelling from absorption of water,bleeding of color into the gel, leakage of fluids from the botanicalsinto the gel and other types of unsightly deterioration have beenobserved in botanicals that have been immersed in a transparent gel.These adverse effects may limit the use of botanicals in decorative gelair fresheners.

SUMMARY OF THE INVENTION

In light of the disadvantages of the prior art, a composition is neededthat will provide a strong, transparent, shiny gel including a volatilecomponent that will evaporate over a predetermined period of time toimpart a desired fragrance to the surrounding environment. The volatileconstituents of the gel may evaporate, under typical householdconditions, over a period from about two weeks to about three months,and particularly from about twenty to about forty-five days, with themost desired period being about thirty days. When the fragrance has beendepleted, the user may replace it with another gel having the same scentselect a differently-scented gel to mark the change of seasons, aholiday or other event, or set a different mood. Preferably, thefragrance is distributed substantially uniformly within the gelcomposition to assist in dispersion of the fragrance into the air at thedesired rate. More importantly, the fragrance constituents are selectedto that the perceived fragrance dispersed into the air remainsconsistent during the desired period of use, without any untowarddiminution of the perceived strength or quality of the fragrance overtime.

The gel must possess a uniform and pleasing appearance when packaged ina transparent container. Thus, the gel must be transparent and free fromparticles or inhomogeneities, such as oil droplets, that are apparentupon visual inspection. It also must possess a uniform texture and acontinuous structure. The ideal gel will have a shiny, elegantappearance. The gel may be colored, if desired, with any of a variety ofnontoxic coloring agents to enhance its decorative effect.

Further, the gel composition must possess low toxicity and flammabilitysuch that it is suitable for household use. A preservative ormicrobiocide may be added to the gel composition to discourage growth ofmicroorganisms that can adversely affect the appearance or fragrance ofthe gel. An aversive agent also may be present to discourage accidentalingestion of the gel.

The gel may be capable of suspending a variety of solids therein tocreate a decorative effect. When the solids to be suspended arebotanicals, the botanicals must retain their natural appearance evenafter immersion in the gel preparation.

Accordingly, it is an object of the present invention to provide a gelcomposition, and a method of preparing the same, suitable for use as adecorative household fragrance source or air freshener. The resultantgel is homogenous and transparent in appearance and possesses a uniformand continuous texture. The gel composition includes fragrant volatilecomponents distributed substantially uniformly throughout thecomposition and capable of evaporating over a predetermined period oftime to impart a desired fragrance to the surrounding environment.

Another object of the present invention is to provide a gel compositionand method of making the same in which the resultant gel is capable ofsuspending a variety of solids therein, and particularly solids in theform of botanicals that retain a natural and attractive appearance evenafter immersion in the gel composition. 4 The foregoing objectives areachieved in a transparent gel composition including a water-solublegelling agent, a fragrance, a surfactant and a cosolvent. The gelcomposition may be prepared by a method that includes the steps ofpreparing a gel mixture comprising the foregoing components and coolingthe gel mixture to a temperature of about 38° C. to about 40° C.Botanicals may be added to the gel mixture before it is cooledcompletely.

These and further objects of the invention will become apparent from thefollowing detailed description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

The above objectives may be achieved in a transparent gel compositionand method of making the same. The composition comprises an aqueous gel,a fragrance, a surfactant and a cosolvent. The aqueous gel includes agelling agent, such as a modified polysaccharide gum. Botanicals may besuspended in the gel composition for decorative effect.

The preferred gelling agent to achieve the desired transparent, shinygel is a modified polysaccharide, for example, a muccopolysaccharide.The gelling agent is crosslinked in the presence of a cationiccrosslinking agent. KelcoGel gellan gum has been used successfully as agelling agent, although other gelling agents also may be used. Cationiccrosslinking agents are preferred for optimum clarity and gel structure.Potassium citrate is the preferred crosslinking agent. Satisfactoryresults also may be achieved with the use of other cationic crosslinkingagents such as water-soluble calcium citrate and magnesium chloride.

The gel composition possesses a suitably low toxicity and lowflammability for its intended use in a household. In some embodiments ofthe present invention, the gel composition may resemble jelly orpreserves, particularly if the composition has a fruity fragrance orpieces of fruit are suspended in the gel. In such instances, an aversiveagent (i.e., a nontoxic substance with a bitter or otherwise unpleasanttaste) may be added to discourage inadvertent consumption of the gelcomposition. Bitrex (dentantonium benzoate) is a preferred aversiveagent.

Under some conditions, the gel composition may provide a suitable mediumfor the growth of microorganisms. The growth of such microorganisms inthe gel typically would cause the gel to develop a sour odor. Moldgrowth also may appear on the surface of the gel. To discourage thegrowth of such organisms and maintain the pleasant fragrance of the gel,a suitable preservative or microbiocide also may be added to the gelcomposition. Kathon microbiocide (a combination ofmethylchoroisothiazolinone and methyl isothiazolinone) is preferred forconvenience and clarity. Satisfactory results also may be achieved usingpotassium sorbate or sodium benroate.

The fragrance is selected so that its bright, effervescent "top notes"are balanced with the heart, or "middle notes." The vapor pressure ofthe fragrance at 20° C. preferably does not exceed 0.1 mm Hg.Preferably, specially denatured alcohol, such as alcohol 40-2, is addedto enhance the fragrance top notes. The specially denatured alcohol,when present, also may assist in solvating the fragrance and maintainingthe initial clarity of the gel composition. The alcohol concentrationpreferably is less that 3% by weight of the gel composition to assist inmaintaining compliance with regulations concerning the emission ofvolatile organic compounds.

A cosolvent, such as dipropylene glycol, may be used to reduce theinterfacial tension between the fragrance oil and water and to assist inthe movement of the oil through the gel matrix. Thus, cosolvents tend tomoderate the evaporation rate of the fragrance and assist in maintaininga consistent odor perception. Preferably, the cosolvent is water-solubleor at least has an affinity for water. In addition to dipropyleneglycol, compounds such as diethyl phthalate, benyzl alcohol, benzylbenzoate, propylene glycol and glyceryl triacetate may be suitable ascosolvents to slow the evaporation rate of the fragrance. Dipropyleneglycol is preferred because it assists it contributes to the clarity ofthe gel product. Compounds that may be suitable for use as cosolvents toenhance the evaporation rate of the fragrance include ethanol andisopropanol.

In addition, the fragrance is selected so that the perceived fragrancedispersed into the air remains consistent during the desired period ofuse, without any untoward diminution of the perceived intensity orquality of the fragrance over time. This may be accomplished, forexample, by a combination of "headspace analysis" and supercriticalfluid extraction techniques. Headspace analysis involves thequantitative and qualitative analysis of the air over fragranced gelcompositions of varying ages to determine the olefactive differencesbetween fresh and aged products. The fragrance may be adjusted to keepthese olefactive differences within an acceptable range, therebyavoiding sour or "off" odors sometimes associated with aged products.Supercritical fluid extraction techniques involve the passing of highpressure carbon dioxide through fragranced gel compositions of varyingages to extract the fragrance from the gel. These extracts are analyzedby gas chromatography to determine the differences in the types andamounts of various fragrance components, and particularly volatileesters, present in the fresh and aged gels as a result of selectiveevaporation. Persons skilled in the art of fragrance formulation andmodification can use the results of these analyses to adjust thefragrance constituents to achieve a result that satisfies consumerexpectations.

The preferred surfactant is a nonionic, ethoxylated alkyl phenol such asRohm & Haas Triton X-102. Nonionic surfactants are preferred because theprovide the best clarity and highest activity. The surfactant shouldhave a low odor and a high hydrophilic-lipophilic balance for optimumsolubilizing of the fragrance oils. Satisfactory results also may beachieved using other nonionic surfactants, such as nonyl phenols andethyoxylated alcohols, with similar properties.

The clarity of the gel product is a function of the amounts of fragranceand surfactant present in the gel composition. Thus, the type or amountof surfactant may require adjustment if the type or amount of fragranceis changed. In addition, when certain surfactants or combinations ofsurfactants are used with particular fragrances, the gel composition maybecome unstable as the temperature of the product is decreased. Thisinstability typically is manifested by a clouding of the product as thetemperature of the product passes below the "cloud point," indicating abreakdown of the oil-water microemulsion. As a result, it may benecessary to adjust the particular surfactant(s) with a particularfragrance to maintain this "cloud point" below a desired temperature.

The table immediately below sets forth illustrative and preferred weightpercents of the components of the gel mixture used in the instantinvention based on the total weight of the mixture:

    ______________________________________                                        Component      Preferred Range                                                                            Illustrative Range                                ______________________________________                                        Deionized water                                                                              79.56                                                          Gelling agent  0.80         0.05-10                                           Crosslinking agent                                                                           0.40         0.001-15                                          Aversive agent 0.05         0-0.1                                             Coloring agents (1% in                                                                       0.14         0-0.2                                             water                                                                         Microbiocide/preservative                                                                    0.05         0-0.1                                             Nonionic surfactant                                                                          6.0          0.5-20                                            Fragrance      5.0          0.1-15                                            Dipropylene glycol                                                                           5.0          0.1-30                                            Alcohol 40-2   3.0          0-3                                               ______________________________________                                    

The gel composition prepared from the preferred components in theabove-described categories results in a product having the desiredattributes when used in conjunction with the process herein described.Suitable gels can be made with components of the gelling system used inamounts shown in the "preferred" range in the above table. However, thecharacteristics of the end product may be slightly modified from thatobtained when the amounts used are in the "illustrative" range.

The method of the present invention includes the steps of:

A. Preparing a suitable liquified gel mixture; and

B. Chilling the gel mixture to a temperature of about 38° C. to about40° C. The term "gel mixture" is used to describe an aqueous gelincluding a gelling agent such as sodium alginate or the like, afragrance, a co-solvent and a surfactant. Botanicals may be suspended inthe gel mixture before it cools completely and gels as described in moredetail below.

The method of making the gel composition may vary to some extentdepending on such factors as the particular constitutents used andwhether the composition is being prepared in a laboratory or acommercial production facility. The description below generally reflectscommercial production of the gel composition. Slightly different stepsused in laboratory production of the gel composition are described inthe Example.

The gel mixture may be prepared by dispersing a modified polysaccharidegum, such as KelcoGel gellan gum, in water. Best results are achievedwhen the water is at about room temperature. It also is possible to addthe gellan gum to warm water, but this increases the likelihood ofagglomeration of the gellan gum before it is completely hydrated.

The resultant dispersion is heated to about 75° C. with stirring orother agitation, preferably in a high shear mixer, until the dispersionbecomes clear and the gel is completely hydrated. The crosslinkingagent, and, if desired, the aversive agent and water-soluble coloringagents may be added to the water either before or after it is mixed withthe gel. The dispersion is maintained at this temperature for about 5 to10 minutes to allow complete dispersal of the gellan gum and ensure goodcrosslinking of the gum. Heating to lower temperatures and/or a shorterholding time may result in formation of a gel that is unacceptably soft.

A fragrance solution may be prepared by combining a surfactant, such asRohm & Haas' Triton X-102 nonionic surfactant, a fragrance, a fragrancecosolvent such as dipropylene glycol, and, if desired, a microbiocide orpreservative. The fragrance solution sometimes is referred to as the"oil phase," although all of its constituents except for the fragranceare water-soluble. These components are stirred or otherwise agitated,preferably for about 10 minutes, until the solution is clear.Preferably, specially denatured alcohol 40-2 is also added to thefragrance solution to enhance the pungency of the top note of thefragrance.

The gel mixture and the fragrance solution are combined and mixed forabout 10 to 15 minutes while the temperature of the mixture is decreasedto about 60° C. The mixture will be milky or opaque upon initialblending at temperatures greater than about 55° C., but will clear asthe temperature approaches about 50° C., indicating that a microemulsionhas been formed.

The gel mixture may be poured into suitable containers. This should bedone while the mixture is warn to avoid congealing of the gel before thecontainers are filled. Use of fluted or textured containers will reducethe likelihood that striations or pores in the gel will be visible,although flat glass containers also may be used. The containers arecooled, for example, in an ice bath or a chilling unit such as a chilltable. When the gel mixture has been chilled to a suitable temperature,typically about 38° C. to about 40° C., the mixture will attain thedesired viscosity or gel structure. The gel will reliquify if thetemperature in increased to about 60° C. or more.

If botanicals are to be added to the liquified gel, they may bepositioned at a desired location within the gel by partially filling thegel container. Generally, the containers should be filled to about onethird to three-fourths fill depending on the desired position of thebotanicals in the container. The partially filled containers are cooledas described above, typically to about 38° C. to about 40° C., until themixture attains a viscosity and/or weak gel structure capable ofsupporting botanicals or other solids placed on the gel surface, suchthat the botanicals will not tend to sink into the gel, but rather willbe maintained in a desired position and level within the container. Ifthe desired viscosity or gel structure is not achieved, however, anysolids intended to be suspended in the gel may tend to float or sinkdepending on the specific gravity of the solids, resulting in anundesirable clumping of the solids in the top or bottom of thecontainer.

The time required for the gel to develop sufficient viscosity to supportbotanicals on its surface will depend on the specific gravity of thebotanicals relative to that of the gel. Less dense botanicals may besupported on a less viscous gel, but denser botanicals will require gelof a higher viscosity for adequate support. For example, dry, delicateflowerheads of Queen Anne's lace typically will require a lowerviscosity, and therefore less chilling time, than moist, densebotanicals such as berries or sliced peaches. The chilling time requiredfor the gel to support low density botanicals may be as short as about10 to 15 seconds for a small, partially filled jar in an ice bath.

When the desired gel structure has been achieved, the botanicals may beadded. Additional warm, liquified gel may be added until the containerhas been filled to the level desired and chilled until the added gelthickens. Care must be taken when adding additional liquified gel toavoid disturbing the desired arrangement of the botanicals or thecontinuous structure of the partially set gel layer. Preferably, thecontainers are allowed to cool to a temperature approaching roomtemperature. The containers may be handled normally without damage tothe gel once the desired temperature is reached. However, extremelyrough handling should be avoided to reduce the likelihood that the gelwill pull way from the container walls.

Any packaging container of reasonable dimension can be employed for thegel preparation consistent with commercial custom. As described above,however, the container preferably is transparent to allow a viewer toperceive the texture and structure of the gel and the distribution ofany solids suspended therein. Glass containers are preferred althoughother transparent container materials also may used to achieve thedesired result.

As the container volume increases, the chilling time required to obtainthe desired gel structure also increases. The maximum preferredcontainer size is in the range of about 100 to 500 ml to promoteeffective cooling of the gel.

The botanicals may be selected so that they retain their naturalappearance after they are immersed in the gel mixture. Botanicalscontaining water-soluble dyes or preservative are unsuitable for use asthe dyes and preservatives tend to cause bleeding of the botanicals intothe gel. This bleeding may be avoided by using botanicals without dyesor preservatives. The botanicals also may be bleached before they areadded to the gel, either to remove natural color that may tend to bleedinto the gel or to create a subtle, ethereal effect. Besides bleaching,the botanicals also may be treated, for example, by freeze-drying themor coating them with a moisture-resistant sealer before they are addedto the gel mixture. The botanicals thus are or are made to becolor-fast, which term is meant to include botanicals as described or astreated above.

EXAMPLE

A transparent yellow gel containing peach slices suspended therein wasprepared in the laboratory as follows:

A. 79.56 weight percent deionized water, 0.4 weight percent potassiumcitrate and 0.05 weight percent Bitrex were combined with 0.09 weightpercent FD&C Red #40 (1.0% in water), 0.03 weight percent D&C Red #33(1.0% in water) and 0.02 eight percent FD&C Yellow #5 (1.0% in water).The resultant solution was mixed until it appeared clear.

B. 0.80 weight percent KelcoGel gellan gum was dispersed into thecolored water solution, and the resulting dispersion heated to atemperature of about 75° C. with stirring until the dispersion becameclear, then cooled to a temperature of about 60° C.

C. 0.05 weight percent Rohm & Haas Kathon was added to the aqueous gumdispersion with stirring until the mixture because clear, whilemaintaining the temperature of the mixture at about 60° C.;

D. A fragrance solution was prepared by combining 6.0 weight percentRohm & Haas Triton X-102 surfactant, 5.0 weight percent fragrance oils,3.0 wight percent alcohol 40-2 6 and 5.0 weight percent dipropyleneglycol with stirring until the solution was clear.

E. The aqueous gum dispersion and the fragrance solution were mixed andblended until the mixture was uniform in appearance, avoiding airentrapment. The resultant mixture was 9 opaque upon initial blending ata temperature greater than about 55° C., but became clear as thetemperature approached about 50° C.

F. The resultant mixture was poured into a container having a capacityof about one-fourth pint until the container was about 3/4 full. Thecontainer was placed into a chilling unit to begin setting up the gel.When an acceptable level of gel viscosity was reached (e.g., uponreaching a at a temperature of about 38° C. to about 40° C.), about 10grams sliced peaches were added. The balance of the container was thenfilled with liquified gel which was allowed to set.

The gel product typically is packaged in a sealed container with aremovable lid. When the lid is removed, the volatile components of thegel evaporate and the fragrance is dispersed into the air over a periodof time. The volatile constituents of the gel may evaporate over aperiod from about two weeks to about three months, and particularly fromabout twenty to about forty-five days, with the most desired periodbeing about thirty days. The uniform distribution of the fragrancewithin the gel aids in dispersion of the fragrance into the air at thedesired rate.

As the volatile components evaporate, the gel will shrink until,eventually, only a residue of essentially nonvolatile components willremain. The fragrance-dispersing capability of the composition willdiminish as the proportion of volatile components decreases. Theshrinkage of the gel therefore provides a user with an visual indicationof when a new supply is needed.

Although a specific embodiment of the invention has been describedherein in detail, it is understood that variations may be made theretoby those skilled in the art without departing from the spirit of theinvention or the scope of the appended claims.

What is claimed is:
 1. A method for making a transparent air freshenercomprising the steps of:mixing together about 0.001-15 wt % potassiumcitrate as a cross-linking agent, an aversive agent, about 0-0.2 wt %color and deionized water to form a first solution, the mixing stepcontinuing until the first solution is clear; dispersing into the firstsolution about 0.05-10 wt % modified polysaccaride gum as a gellingagent to form a dispersion; heating the dispersion to above 60° C. andstirring the dispersion until the dispersion is clear; after thedispersion is clear, cooling the dispersion to about 60° C.; mixingtogether an initial mixture of about 0.5-20 wt % nonionic surfactant,about 0-3.0 wt % SD alcohol, about 0.1-30 wt % dipropylene glycol as aco-solvent and about 0.1-15 wt % fragrance until the initial mixture isclear; mixing the initial mixture with the dispersion at a temperaturegreater than about 55° C. to form a resulting mixture and then coolingthe resulting mixture until the resulting mixture becomes a clearmixture; pouring the resulting mixture into a transparent container; andchilling the transparent container, said phase being free from cloudingwith resulting mixture to form a transparent, homogenous gel having onephase in the container; the fragrance being present in an amount toprovide a vapor pressure at 20° C. of not more than 0.1 mm Hg, thenonionic surfactant being in an amount to form the transparent gelhaving one phase, the co-solvent being in an amount to moderateevaporation of the fragrance so that the transparent gel acts to freshena room by evaporation of the fragrance, said fragrance being releasedover a period of at least two weeks.
 2. A method according to claim 1,including heating the dispersion to about 75° C.
 3. A method accordingto claim 1, including chilling the resulting mixture to about 38-40° C.4. A method according to claim 1, wherein the surfactant is TritonX-102.
 5. A method according to claim 1, wherein the gelling agent isgellan gum.
 6. A method according to claim 1 including partially fillingthe transparent container with the clear mixture; chilling the clearmixture to set the transparent gel; thereafter inserting the solids intothe set gel; and thereafter adding additional clear mixture to cover thesolids and complete the air freshener, the transparent gel appearing asone phase and suspending the solids in the one phase, without anyseparation being visible between the clear mixture portions added to thetransparent container.